An illustrative hydrofoil watercraft has submerged strut-supported foils which move through the water during flight, i.e., during foil-borne operation of the craft the foils develop lift comparable to an airplane wing. Such craft may be operated at relatively high speeds by means of, e.g., a waterjet propulsion system. In such a system water is drawn or ingested into a water intake and directed to a pump which accelerates and discharges the water rearwardly in a high velocity jet resulting in a forwardly directed propulsion force.
Such a hydrofoil craft may be moored in relatively shallow water by retracting the struts into recesses appropriately located in the bow and stern of the craft. Experience has found that the accumulation of surface debris in the vicinity of a moored hydrofoil craft can cause serious problems especially when the craft employs a waterjet propulsion system. Surface debris can either be sucked from the surface of the water into the water intake, ingested or lodged in the waterjet propulsion system or can interfere with the strut actuation mechanism resulting in unscheduled delays and potentially costly repairs. In addition, debris can cause a blockage of the seawater cooling system of the watercraft (if so equipped) resulting in damage or loss of equipment being cooled on the watercraft.